Grid structure



Dec; 23, 1958 J. s. DE WlTT GRID STRUCTURE Filed Feb. s, 1956 A B F INVENTOR: JON s. deWlTT, lav/77W,

HIS ATroR' EY.

GRID STRUCTURE Jon S. de Witt, Rexford, N. Y., assignor to General Electric Company, a corporation of New York Application February 6, 1956, Serial No. 563,492

Claims. (Cl. 313-248) This invention relates to grid structures for use in connection with high frequency apparatus and more particularly to novel grid structures for klystrons.

A detailed explanation of the klystron construction and operation is readily found in the literature as for instance Radio Engineers Handbook by F. E. Terman, published by McGraw-Hill Book Company Inc., 1943. As is well known, klystrons are velocity modulation electron discharge tubes having a structure which utilizes bunching of the electron beam for its operation. Bunching of the electron beam is accomplished by passing an electron beam through a pair of closely spaced buncher grids each of which is connected to one side of a tuned circuit. An alternating voltage developed across the tuned circuit causes the velocity of the electrons leaving the buncher grids to differ in aperiodic manner thus bunching the electrons. A second tuned circuit or, catcher grid circuit, is located at a distance at which electron bunching is maximum to absorb energy from the electrons. For work at high frequencies the tuned circuits of the buncher and the catcher usually are cavity resonators.

A problem associated with grid structures for use in klystrons is that of providing a uniform electric field in the center region of the klystrons, in that region through which the electron beam passes. The electric field must be uniform to obtain proper bunching of the electrons to assure proper transfer of energy to the catcher grid, and thus proper operation of the klystron. Radial vanes or ribbons are generally employed in the fabrication of grid structures for higher power tubes and fine wire mesh is generally employed for low power tubes. The use of vanes is preferred for the higher power tubes since a minimum number of electrons are intercepted providing a more efficient transfer of energy and decreasing the heat dissipation problem. The flat portion of the vanes is substantially parallel to the axis of the electron beam, and the narrow portion of the vanes is substantially perpendicular to the beam axis, thus while only a minimum number of electrons will be intercepted, there is available a maximum area for purposes of heat dissipation.

Various grid structure configurations comprising vane members have heretofore been attempted in an effort to obtain uniform fields in the above mentioned center region. Heretofore, the grid structures have included individual rod or vane members projecting toward the axis of the electron beam. Heretofore, individual rod members were believed to be superior in performance since an individual member would present a minimum beam interception area to the electron beam; this was believed particularly important in the outer portions of the grid structure corresponding to the outer field regions due to the fact that in said outer field regions the electrons will travel in paths which are less parallel to the axis of the beam and a greater number of electrons will tend to impinge on any interposed grid structure.

However, the individual rod or ribbon members have the disadvantage that said members are in effect unsupite States Patent 0 ported at one end. As a result, said individual rod or vane members tend to be easily and undesirably deflected or distorted by physical or thermal means. Such physical deflections and distortions adversely effect the uniformity of the field, resulting in a varying field which produces irregular bunching of the electron beam.

As previously stated, while various configurations of vanes have been attempted, a rigid vane structure having good heat dissipation characteristics and having the properties of producing a uniform field has not heretofore been described.

It is, accordingly, a principal object of the present invention to provide a novel grid structure for producing a uniform field in the gap region of cavity resonator klystron tubes.

It is another object of my invention to provide a novel grid structure for use in an electric field.

It is another object of my invention to provide an improved rigid grid structure.

In the attainment of the foregoing objects of my invention, I provide a novel grid structure comprising a plurality of V-shaped members extending radially toward a common center.

Other objects and advantages will be apparent after a consideration of the specification and the drawings in which:

Figure 1 is a partially exploded isometric view of the grid structure of the present invention;

Figure 2 is a schematic diagram of a klystron embodying the grid structure of the invention; and

Figure 3 is a detailed illustration of a modified form of grid member.

In Figure 1, grid 11 is formed with a circular outer frame or rim member 12, having radially extending grooves 13, a plurality of relatively large V-shaped members or vanes 14 and a plurality of substantially smaller V-shaped members or vanes 15. Grooves 13 are adapted to receive vanes 14 and 15 such that the outer edges of the vanes are flush with the grooved surface of frame 12. V-shaped vanes 14 and 15 may be affixed to frame 12 by inserting the vanes in the respective grooves 13 and brazing the vanes to the frame. Said vanes extend radially inwardly toward the axis of the beam A-A', Figures 1 and 2. The V-shaped vanes are formed of a sheet material to provide a vane type structure with the wider dimension extending parallel to the axis of the rim for presenting minimum electron interception area while obtaining maximum heat dissipating area, as discussed above.

Figure 2 shows a klystron 19 of the multiple cavity resonator type and in which the grid structures 11 are in accordance with my invention.

The gun 21, resonator cavities 16 and 18, and collector electrode 17 can be of any suitable conventional design well-known to those skilled in the art. As shown, the grids 11 are suitably secured as by brazing or silver soldering to the envelope of the tube in the gap region of the resonators.

In a preferred form, grid 11 comprises four relatively large V-shaped vanes 14 spaced in quadrature about frame 12 with the open ends of the vanes 14 attached to said frame and the closed ends of the vanes 14 extending toward the axis, A-A', but defining an open space in the center. Because frame 12 is grooved at each place where a vane attaches to said frame, excellent rigidity is obtained and further unwanted protrusions as for example, brazing materials or the like are not apt to extend into the electric field region. Further, inserting the vanes into the formed grooves assures that the vanes are positioned in a plane perpendicular to the axis of the electron beam. V-shaped vanes 15 are interposed between and within vanes 14. An exploded view of one vane 15 is shown to indicate the construction of the vanes; vanes 14 are of similar construction, although larger. Each one of vanes 14 surrounds a small vane 15, and one small vane 15 is also afiixed to the rim between each of the vanes 14. The configuration of large V-shaped vanes 14 surrounding smaller V-shaped vanes 15 and having said large V-shaped vanes 14 separated by the smaller vanes 15 assures a uniform field, and yet offers a minimum of intercepting surfaces to the electron beam which is normally most concentrated in the center region. The V- shapes of the included members provide rigidity to the structure by utilizing essentially triangular structures which inherently have good rigidity.

Figure 3 shows a vane construction useful in the grid of my invention, and .in which the bight portion of the vanes is formed with a more pronounced curvature. This form is somewhat more economical to produce and has been found to be substantially as effective as the V-shaped vanes of Figures 1 and 2.

It will be understood that although the invention has been discussed in detail for use in a klystron, the grid structure is not limited in application thereto but can be used wherever a grid structure is necessary in a field region which is to be traversed by electrons.

While specific examples have been given in describing details of this invention, it will be understood that they have been given merely by way of illustration and that the invention is to be construed as including other modifications within the true spirit and scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A grid structure for use with electron beam tubes, comprising V-shaped vanes, a frame comprising only a single annular wall having a plurality of relatively elongated grooves in a'transverse surface thereof and extending radially therethrough, the free ends of said V-shaped vanes being positioned in said grooves in said frame flush with the grooved surface of said frame, and said free ends being brazed to said frame only at points disposed outwardly of the region defined by the internal surface of said frame.

2. A klystron grid structure comprising a plurality of arrays of relatively large and smaller radially extending metallic vanes each of which vanes is of generally V- shaped construction, an outer frame, and the free ends of said vanes being afiixed to said frame with the smaller of said vanes each being disposed between pairs of said large vanes.

3. A klystron grid structure comprising an outer frame, a first group of V-shaped radially extending metallic vanes, the free ends of said V-shaped vanes afiixed to said frame, said V-shaped vanes affixed in quadrant points relation, a second group of V-shaped vanes relatively smaller than said first V-shaped vanes, one each of said second group of V-shaped vanes being disposed within respective ones of said first V-shaped vanes, and additional ones of said second group of V-shaped vanes being disposed between pairs of vanes of said first group of V- shaped vanes.

4. A grid structure comprising an outer frame having grooves therein, a plurality of inwardly extending V- shaped vanes having the free ends of said V-shaped vanes affixed in said grooves, said V-shaped vanes comprising first and second vanes, said second vanes substantially smaller than said first vanes, said second vanes afiixed to said frame within and between said large vanes.

5. A klystron grid structure comprising an outer frame including a plurality of circumferentially spaced grooves in a planar surface thereof, a first group of generally V- shaped radially extending metallic vanes corresponding in thickness to the depth of said grooves, the free ends of said vanes being disposed in said grooves and brazed to said frame only at points disposed outwardly of the region defined by the internal surface of said frame, said vanes affixed in quadrant points relation, a second group of generally V-shaped vanes relatively smaller than said first group of vanes and secured to said frame in the same manner as said first group, one each of said second group of vanes being disposed within respective ones of said first group of vanes, and additional ones of said second group of vanes being disposed between each of said first group of vanes.

References Cited in the file of this patent UNITED STATES PATENTS 2,460,120 Bondley Ian. 25, 1949 2,515,267 Salisbury July 18, 1950 2,738,438 Shepherd Mar. 13, 1956 

